Yankee hood performance studies; The effect of air balance on thermal efficiency

With today's ever-increasing production rates on tissue-grade machines, many mills experience a need to increase the contribution of Yankee hoods to drying. Until the cylinder is replaced, its contribution to drying is fixed at its maximum drying rate. Consequently, the hoods should be checked routinely to ensure that they run optimally. Most air systems are not gas-or oil-fired, in contrast to the original steam-heated designs. As a result, Yankee air systems are energy intensive. A proper hood balance ensures minimum thermal consumption, or optimum thermal efficiency. Thermal efficiency is defined as the Btu's consumed by the burner per pound of water evaporated by hood. A simple engineering survey, or system examination, allows the papermaker to verify hood performance and balance the air system. In this paper typical data from a such a survey are shown. These surveys can often lead to considerably savings in burner fuel.